Axially and radially compensated high pressure gear pump

ABSTRACT

An axially and radially pressure compensated internally-geared high pressure gear pump in which the filler member is commashaped and abutted against a large supporting pin under operating pressure, the abutment position being maintained under dry run conditions by an elastically deformed pin biasing the filler member against the supporting pin, while allowing for radial adjustments of the filler member position.

United States Patent Eckerle June 17, 1975 [54] AXIALLY AND RADIALLYCOMPENSATED 3,525,580 8/l970 Eckerle 4l8/7l "1G" PRESSURE GEAR PUMPR27,90I I974 Eckerle 4|8/7l [76] Inventor: Otto Eckerle, Benzstrasse 6,7502 FOREIGN PATENTS OR APPLICATIONS Malsch' Germany 1.403923 11 /I969Germany 1. 418/169 [22] Filed: Mar. 18, 1974 [21] Appl. No.: 452,282Primary Examiner-John J. Vrablik Attorney, Agent, or Firm-Joseph A.Geiger [30] Foreign Application Priority Data Mar. 16, 1973 Germany2313085 [57] ABSTRACT [52] U S Cl 4l8/7l 8/131, 418/126 An axially andradially pressure compensated internal- 4ls/69 ly-geared high pressuregear pump in which the filler [51] Int. CLHM F02: 21/00 Folc 1/10, Folc19/02 member is comma-shaped and abutted against a large [58] Field 0Search iiiii U MS/H 72 31 132 supportmg pin under operating pressure,the abutment i position being maintained under dry run conditions by anelastically deformed pin biasing the filler member [56] References Citedagainst the supporting pin, while allowing for radial adjustments of thefiller member position. UNITED STATES PATENTS 3,289,599 l2/l966 Eckerleet al 418/126 10 Claims, 4 Drawing Figures a 7 i l PATENTEDJUN17 I975890,065 SHEET 2 Fig.4

AXIALLY AND RADIALLY COMPENSATED HIGH PRESSURE GEAR PUMP BACKGROUND OFTHE INVENTION 1. Field of the Invention The present invention relates togear pumps, and in particular to high pressure gear pumps of theinternally-geared type having both radial and axial pressurecompensation means.

2. Description of the Prior Art High pressure gear pumps of theinternally-geared type normally consists of a housing, a central mainbore, a pinion axially journalled inside the housing, and an internallytoothed gear ring engaging the pinion, with a filler member positionedbetween the teeth of the pinion and gear ring. It is known, for example,from my US. Pat. No. 3,525,581, reissued under N0. Re 27,904, to provideradial pressure compensation means in this type of high pressure gearpump, by arranging a so-called control piston between the radiallydisplaceable gear ring and the housing, in opposition to the hydraulicthrust which is generated by converging teeth of the rotating gears.This control piston is subjected to one or several compensation pressurefields urging the piston against the gear ring, which in turn bearsagainst the filler member and against the pinion, or in some casesagainst a stop which limits the depth of tooth engagement.

It is further known from my aforementioned patent to provide axialpressure compensation means, using axially displaceable discs on eachside of the pinion and gear ring, which discs are pressed against theflanks of the pinion and ring under the influence of axial compensationpressure fields arranged between these axial discs and the housing. Theincorporation of radial and axial pressure compensation means in theinternallygeared pump makes it possible to use as a filler member asimple wedge-shaped member, rather than the previously commonsickle-shaped filler member. Due to the radial pressure compensationaction, which assures clearance-free interaction between the pinion,filler member and gear ring, the area of the filler member which isexposed to the hydraulic pressure is relatively small. However, in spiteof this small effective area, the filler member is neverthelesssubjected to a force pushing it back, i.e. against the direction of gearrotation. Under very high pressures, these forces can becomeconsiderable, requiring appropriately resistant and stiff supportingmeans for the filler member on the housing walls. In theearlier-mentioned prior art pump of this type, the filler memberincludes a pin which extends axially through it and into both sides ofthe housing, thereby fixing the position of the filler member in bothrotational directions. This arrangement has the disadvantage ofnecessitating a limitation of the diameter of the tiller membersupporting pin, while weakening the ramaining cross section of thefiller member.

Although the arrangement with the supporting pin extending through thefiller wedge is satisfactory under normal operating conditions, showingonly a very small deformation under high pressure operation, it wasfound to present a shortcoming under dry run conditions, when the normalhydrostatic biasing force on the filler member is not present, and whenincreased friction between the gear teeth and the filler member surfacestakes place. In this situation, the supporting pin cannot prevent thisfrictional engagement, and the filler member is drawn between the pinionand gear ring in a wedging action.

In the known gear pump disclosed in my US. Pat. No. Re 27,904, thisforward rotation is prevented with the help of a second axial pinextending through the filler wedge into the axial discs of the axialpressure compensation means. However, when the pump design calls for thecontrol piston to be radially supported not only on the filler member,but primarily on the axial discs, extremely tight manufacturingtolerances are necessary, unless the filler member is initially providedwith a small excess thickness to be worn off in a run-in operation. Sucha run-in operation in turn increases the testing and quality controlcosts of pump production.

SUMMARY OF THE INVENTION It is an objective of the present invention tosuggest an improvement over the prior art devices of this type, byeliminating some of the earlier-mentioned shortcomings and byconsequently realizing savings in manufacturing and testing expense.

The invention proposes to attain the objective by suggesting a highpressure gear pump of the above type in which the filler member isshortened to a commashaped filler member, the back side of which issupported against an axially extending supporting pin of maximumdiameter in a known manner, and in which a second, elastic pin extendsthrough the filler member and serves as a spring, urging the fillermember rearwardly against the supporting pin. The bias exerted on thefiller member by the elastic pin prevents the filler member from beingdrawn in the direction of rotation and wedged between the teeth of thepinion and gear ring under dry run conditions.

An additional advantage offered by this novel arrangement is realizablein connection with axial discs which are rotationally fixed in relationto the housing, where, through selection of a supporting pin ofappropriate thickness on its abutment face, the manufacturing tolerancesof the filler member, of the two gears, and of the two axial discs canbe conveniently balanced so that the control piston compensationpressure is distributed between, and born by the axial disc and thefiller member. Since it is much less expensive to grind the abutmentfaces on these pins to different dimensions than to use a run-inoperation to achieve this same balance, a saving in manufacturing costsis realized.

BRIEF DESCRIPTION OF THE DRAWINGS Further special features andadvantages of the invention will become apparent from the descriptionfollowing below, when taken together with the accompanying drawingswhich illustrate, by way of example, an embodiment of the invention,represented in the various figures as follows:

FIG. I shows a gear pump embodying the invention, as seen in a radialcross section taken along line I-l of FIG. 2;

FIG. 2 shows an axial cross section of the gear pump of FIG. 1 takenalong line IIII thereof;

FIG. 3 shows a detail of the pump of FIGS. 1 and 2 in a partial axialcross section taken along line III-Ill of FIG. I; and

FIG. 4 shows in a partial cross section similar to that of FIG. 3 amodification of the embodiment of FIGS. 1-3.

DESCRIPTION OF THE PREFERRED EMBODIMENT The high pressure gear pump ofPK]. 1 shows an externally geared pinion 1 engaging an internally gearedgear ring 2 for clockwise rotation, the gear ring 2 being arranged in afloating mode so as to engage the pinion without tooth flank clearance.This ring is held in position by means of a control piston 3 which isbiased radially inwardly by means of three circular compensationpressure fields 4. These compensation pressure fields 4 are constitutedby short pistons 4' located in matching recesses inside the controlpiston 3 and sealed thereagainst by means of gaskets 5. On their backside, the pistons 4' are supported on the bore surface of the pumphousing 6. The radially inwardly directed compensation pressure on thecontrol piston 3 created by the compensation pressure fields 4 issomewhat in excess of the radially outwardly directed thrust exerted onthe gear ring 2, causing the latter to be biased against the pinion land against a filler member 7 which is located between the convergingteeth of the pinion 1 and gear ring 2. The filler member 7 in turn isrotationally abutted against a supporting pin 8 which prevents thefiller member 7 from moving against the direction of rotation under thehydrostatic forces impinging on its tip portion. The tooth crownsurfaces of the pinion 1 and gear ring 2 are thus maintained in sealingand gliding contact with the inner and outer surfaces of the fillermember 7. The orientation of the abutment face 8' in relation to theoutline of the filler member 7 is preferably perpendicular to thedirection of control piston bias against the gear ring 2 and the fillermember 7.

In FIG. 2, the axially cross-sectioned pump shows, in addition to thepinion 1, the gear ring 2, and the control piston 3, two axial discs 9and 10, arranged to axially adjoin the pinion l and gear ring 2. Theseaxial discs 9 and 10 cooperate with axial pressure compensation means inthe form of pressure fields l2 and 13 milled into the correspondingfaces of the housing 6 and of the housing cover 11. O-rings l4 and 15positioned inside these compensation pressure fields l2 and 13 provide aseal along the outline of each field. The axial compensation pressureexerted by these fields against the axial discs 9 and 10 force themagainst the flanks of the pinion 1 and gear ring 2 for clearancefreesealing contact. The control piston 3 not only bears against the fillermember 7, through the gear ring 2, but is also supported against theaxial discs 9 and 10, and through the latter against the shaft of pinionl, by axial shoulders on the control piston reaching axially over thewidth of the gear ring into engagement with appropriate abutmentsurfaces on the axial discs 9 and 10.

The arrangement of the supporting pin 8 for the filler member 7 isillustrated in more detail in FIG. 3 where the housing 6 and the housingcover 11 are shown to include appropriate seating bores 16 and 17,positioning the pin 8. The latter is flattened on one side to present anabutment face 8' against the filler member 7. This supporting pin 8 isas large in diameter as the space between the pinion l and gear ring 2permits, in order to minimize its lateral deflection under thehydrostatic forces acting on the filler member 7, which forces have to etransmitted to the housing parts by pin 8.

The axial discs 9 and 10 are rotationally positioned relative to thehousing parts 6 and 11 by means of two positioning pins 18 and 19. Thesepositioning pins, pressed into the respective housing parts, are hollowfor the accommodation of a thin, elastic pin 20 which extends axiallythrough a bore 21 in the filler member 7. The corresponding bores insidethe positioning pins 18 and 19 are ofi'set in the rotational directionin relation to the bore 21 in the filler member 7, so that the elasticpin 20 needs to be bent for assembly, thereby creating a spring bias onthe filler member 7 against the supporting pin 8. The diameter of thefiller member bore 21 is preferably larger than would be necessary, andcorrespondingly further offset in the circumferencial direction, so asto render it less sensitive to manufacturing tolerances and to allow forradial repositioning of the filler member 7 in relation to the pinion l.The bores inside the positioning pins 18 and 19 and inside the fillermember 7 are appropriately tapered or otherwise widened, in order toaccommodate the deflection of the elastic pin 20. The latter isconveniently made of spring steel (piano wire) so as to permit evenexcessive deflection, as during assembly operations, for example.Instead of positioning the pin extremities in side the hollow pins 18and 19, it is of course also possible to locate the disc positioningpins elsewhere and to provide separate positioning bores in the housingparts 6 and 11, or preferably, to provide oblong positioning recesseswhich permit the aforementioned radial repositioning.

The axial discs 9 and 10 have on their outer periphery a semi-circularrecess, the abuting shoulder portions of the control piston 3 havingsimilar semicircular recesses which match the recesses in the axialdiscs 9 and 10 for the accommodation therein of short pins 22 and 23fixing the control piston 3 rotationally in relation to the axial discs,and through their positioning pins 18 and 19 in relation to the housingparts 6 and 11.

In Fig. 4 is illustrated a modified embodiment of the invention in whichthe short pins 22 and 23 of P16. 3 are replaced by longer positioningpins 24 and 25 which are pressed into the housing parts 6 and 11 so asto directly position the axial discs 9 and 10 and the control piston 3in the rotational direction. In this case, it is possible to use ashortened elastic pin 26 whose extremities, instead of being supportedinside hollow pins pressed into the housing parts, are directlysupported inside bores in the axial discs 9 and 10.

It should be understood, of course, that the foregoing disclosuredescribes only preferred embodiments of the invention and that it isintended to cover all changes and modifications of these examples of theinvention which fall within the scope of the appended claims.

I claim:

1. In a high pressure gear pump of the internallygeared type having apinion, a cooperating gear ring, and a radially displaceable fillermember arranged in the main bore of the pump housing, with a radiallypressure-compensated control piston biasing the gear ring radiallytoward the pinion and the filler member, and with axiallypressure-compensated discs bearing against the axial flanks of thepinion and gear ring in at least the area of pressure generation, thecombination of:

means for abutting the filler member relative to the pump housingagainst back movement in the rotational direction opposed to thedirection of gear rotation, while permitting a small radial displacementof the filler member; and

mechanical spring-biasing means engaging the filler member for biasingthe latter toward said abutting means in said abutment direction, whilepermitting said radial displacement of the filler member.

2. A combination as defined in claim 1, wherein:

the filler member biasing means is a bendable, relatively thin elasticpin extending axially through the filler member and into the axialdiscs;

the axial discs include means for positioning the extremities of saidpin; and

the pump housing includes means for rotationally positioning the axialdiscs.

3. A combination as defined in claim 1, wherein:

the filler member is comma-shaped in its general cross-sectionaloutline, having a substantially flat end face at its wider extremityoriented in said abutment direction;

the filler member abutting means is a rigid abutment pin mounted in thepump housing and extending axially across its bore in the space betweenthe toothed peripheries of the pinion and internal gear ring.

4. A combination as defined in claim 3, wherein:

said abutment pin is cylindrical and has a peripheral portion of itscross section removed to form an abutment face for engagement with saidfiller member end face.

5. A combination as defined in claim 4, wherein:

the abutment face on the abutment pin and the cooperating end face ofthe filler member form a plane of abutment which is substantiallyperpendicular to the direction of control piston bias against the gearring and filler member.

6. A combination as defined in claim 4, wherein:

the pinion has a bearing portion adjacent its axial flanks;

the axial discs have a shape which includes an inner radius portionengaging said pinion bearing portion and an outer radius portion whichis engaged by the control piston for radially inwardly abutting thelatter;

the control piston has two axially extending shoulder portions for saidabutting engagement with the axial discs; and

the radial height of the abutment face on the abutment pin in relationto the mounting location of the pin in the housing is such that thecontrol piston compensation pressure is distributed between, and born bysaid pinion bearing portion, via the axial discs, and the pinion teeth,via the gear ring and the comma-shaped filler member.

7. A combination as defined in claim I, wherein:

the tiller member biasing means is a bendable, rela tively thin elasticpin extending axially through the filler member and through the axialdiscs into the pump housing on both sides of the gears;

the pump housing includes means for positioning the extremities of saidpin; and

the tiller member includes an axial bore for said elastic pin, said borebeing offset in relation to said pin positioning means in such a way asto require biasing deflection of the pin away from said abutmentdirection, said bore further being enlarged to accommodate saiddeflection and to allow a small displacement of the tiller wedge in theradial direction, without affecting the operation of the biasing means.

8. A combination as defined in claim 7, wherein:

said pin positioning means in the pump housing is in the form of twoelongated recesses permitting radial shifting of the elastic pin inconformance with radial displacements of the filler member.

9. A combination as defined in claim 7, wherein:

said pin positioning means in the pump housing is in the form of hollowpositioning pins which also serve to rotationally position the axialdiscs, the positioning pins having an enlarged outer bore portion toaccommodate the biasing deflection of the elastic pin.

10. A combination as defined in claim 7, wherein:

said elastic pin is a length of spring steel rod.

1. In a high pressure gear pump of the internally-geared type having apinion, a cooperating gear ring, and a radially displaceable fillermember arranged in the main bore of the pump housing, with a radiallypressure-compensated control piston biasing the gear ring radiallytoward the pinion and the filler member, and with axiallypressure-compensated discs bearing against the axial flanks of thepinion and gear ring in at least the area of pressure generation, thecombination of: means for abutting the filler member relative to thepump housing against back movement in the rotational direction opposedto the direction of gear rotation, while permitting a small radialdisplacement of the filler member; and mechanical spring-biasing meansengaging the filler member for biasing the latter toward said abuttingmeans in said abutment direction, while permitting said radialdisplacement of the filler member.
 2. A combination as defined in claim1, wherein: the filler member biasing means is a bendable, relativelythin elastic pin extending axially through the filler member and intothe axial discs; the axial discs include means for positioning theextremities of said pin; and the pump housing includes means forrotationally positioning the axial discs.
 3. A combination as defined inclaim 1, wherein: the filler member is comma-shaped in its generalcross-sectional outline, having a substantially flat end face at itswider extremity oriented in said abutment direction; the filler memberabutting means is a rigid abutment pin mounted in the pump housing andextending axially across its bore in the space between the toothedperipheries of the pinion and internal gear ring.
 4. A combination asdefined in claim 3, wherein: said abutment pin is cylindrical and has aperipheral portion of its cross section removed to form an abutment facefor engagement with said filler member end face.
 5. A combination asdefined in claim 4, wherein: the abutment face on the abutment pin andthe cooperating end face of the filler member form a plane of abutmentwhich is substantially perpendicular to the direction of control pistonbias against the gear ring anD filler member.
 6. A combination asdefined in claim 4, wherein: the pinion has a bearing portion adjacentits axial flanks; the axial discs have a shape which includes an innerradius portion engaging said pinion bearing portion and an outer radiusportion which is engaged by the control piston for radially inwardlyabutting the latter; the control piston has two axially extendingshoulder portions for said abutting engagement with the axial discs; andthe radial height of the abutment face on the abutment pin in relationto the mounting location of the pin in the housing is such that thecontrol piston compensation pressure is distributed between, and born bysaid pinion bearing portion, via the axial discs, and the pinion teeth,via the gear ring and the comma-shaped filler member.
 7. A combinationas defined in claim 1, wherein: the filler member biasing means is abendable, relatively thin elastic pin extending axially through thefiller member and through the axial discs into the pump housing on bothsides of the gears; the pump housing includes means for positioning theextremities of said pin; and the filler member includes an axial borefor said elastic pin, said bore being offset in relation to said pinpositioning means in such a way as to require biasing deflection of thepin away from said abutment direction, said bore further being enlargedto accommodate said deflection and to allow a small displacement of thefiller wedge in the radial direction, without affecting the operation ofthe biasing means.
 8. A combination as defined in claim 7, wherein: saidpin positioning means in the pump housing is in the form of twoelongated recesses permitting radial shifting of the elastic pin inconformance with radial displacements of the filler member.
 9. Acombination as defined in claim 7, wherein: said pin positioning meansin the pump housing is in the form of hollow positioning pins which alsoserve to rotationally position the axial discs, the positioning pinshaving an enlarged outer bore portion to accommodate the biasingdeflection of the elastic pin.
 10. A combination as defined in claim 7,wherein: said elastic pin is a length of spring steel rod.